(CBS) — It has been three weeks since an 86-year-old Morton Grove man was killed in a hit-and-run crash not far from his home and now police say they are making some progress in the investigation.

Found at the scene of that hit-and-run: debris from a headlight and debris from a bumper. All found near the spot in Morton Grove where 86-year-old Richard Mikulec was hit the night of January 12.

Now Police Commander Paul Yaras says investigators have been able to take a look at those objects and narrow the search for the hit-and-run vehicle and they know it’s a GM full-size van or truck.

“What we believe we’re looking for is possibly a 2008 to 2012, either Chevy Express or possibly a GMC Savana. But the bumper that is on those types of vehicles is also on GM box-type trucks. So we’re not going to limit ourselves at this point.”

Commander Yaras says investigators have been able to narrow the search from hundreds of thousands of vehicles to about 700.

Richard Mikulec’s son wrote about his father in an obituary, saying he was a chemist who worked for Searle for years – and spent much of his life working on artificial sweeteners.